1. Field of the Invention
The present invention relates to a copying machine which comprises a recirculating document feeding apparatus for sequentially and circulatorily feeding and transporting a sheet document to a reading station where document images are to be read and effects copying operation in various copying modes in cooperation with the document feeding apparatus.
2. Description of the Prior Art
In recent years, copying machines have been provided with document feeding apparatus for feeding a plurality of documents sequentially to a reading station below which exposure means for reading document images is disposed in order to copy effectively a plurality of document sheets of same size. Particularly, such a document feeding apparatus is referred to as a recirculating document feeding apparatus, in which the documents placed in a document placing member are fed therefrom, transported to the reading station, and then returned to the placing member again. In this way, the documents are fed circulatorily in the recirculating document feeding apparatus.
With such a recirculating document feeding apparatus as described above, both sides of the document are fed to the reading stations with faced to corresponding reading stations. The document image read at the reading station is copied onto recording paper in the copying machine cooperating with the feeding apparatus. Thereby, various copying modes can be effected, such as a mode in which the documents having images on both sides thereof (hereinafter referred to as a duplex document) are copied correspondingly onto one or both sides of the recording paper (hereinafter referred to as a duplex copy) or another mode in which the documents having an image on one side thereof (hereinafter referred to as a simplex document) are copied onto both sides of the recording paper.
For example, in case of obtaining the duplex copy from the simplex document, the recirculating document feeding apparatus feeds a plurality of documents one by one to the reading station. In the copying machine, the document image exposingly read from one side of the document is formed into a latent image onto, for example, a photoreceptor rotating at a constant speed, and further developed into a toner image, which is copied onto one side of the fed recording paper. The recording paper to one side of which the copying operation has been effected is temporarily stored in an intermediate tray, then fed to the photoreceptor again. Thereupon, the document image read from the document fed to the reading station succeedingly to the document whose image has been copied onto one side of the recording paper is copied onto the other side of the recording paper. Consequently, the recording paper is discharged. In this way, duplex copies can be obtained from a plurality of simplex documents.
In the case where the duplex copies are obtained from the simplex documents, there are two copying processes. One is to copy the precollated simplex documents with respect to page number thereof from the last paged document. The other is to copy the similar documents from the first paged document. In the former case, the copying operation requires to be changed depending on whether the number of the documents is odd or even. More specifically, in the case where the number of the documents is even, a completely collated duplex copy set can be obtained just by copying the document images of the simplex documents sequentially onto both sides of the recording paper. However, in the case where the document images of the simplex documents are sequentially copied onto the recording papers in a similar manner as in the case where the document number is even, the other side of the recording paper, to one side of which the document image of the first page is copied, is blank and thereby a collated duplex copy set cannot be obtained.
Accordingly, the copy operator counts the number of the documents beforehand, and causes to switch to an appropriate copying process by inputting the information indicative of whether the number of the documents is odd or even through the use of a control panel. Alternatively, a plurality of documents placed in the placing member are circulated through the transporting path past the reading station without being copied, and thereby effecting the counting operation for automatically counting the number of the documents by means of sensors or the like.
Imposing the counting operation on the copy operator makes the copying operation cumbersome. Particularly, in the case where a large number of documents are to be copied, the copying operation becomes further burdensome and is liable to miscount the number of the documents.
On the other hand, the counting operation by transporting the documents without being copied in the recirculating document feeding apparatus does not involve a cumbersome operation, hence having been utilized in recent years. Besides a (simplex.fwdarw.duplex) mode, the counting operation can be effected in the cases which requires counting of the number of the documents beforehand, such as a blank paper inserting mode. In the blank paper inserting mode, a blank recording papers is inserted every plural number of copied recording papers.
The copying modes of the copying machine generally includes a standard mode in which the document image of the document is copied onto the recording paper in same size, a reduction mode in which the document image is copied onto the recording paper with reduced the size thereof, and a enlargement mode in which the document image is copied onto the recording paper with enlarged the size thereof. In the reduction and enlargement modes, transporting speed of the document past the reading station relative to the photoreceptor rotating at a constant speed is appropriately adjusted. Thereby, the size of the document image read onto the photoreceptor is controlled. In this way, magnification at which the document image is copied onto the recording paper is set in the respective copying mode.
The transporting speed of the documents sequentially transported without being copied in the counting operation has been set at a constant transporting speed at which the documents are transported to the reading station to be copied. More specifically, despite the fact that the transporting speed at which the document is transported to the reading station can be variable in accordance with the respective copying magnification, the constant transporting speed of the document in the counting operation is set equal to the transporting speed to the reading station in the standard mode. Accordingly, since the documents are transported without being copied at the constant transporting speed in accordance with the standard mode despite the capability of transporting the document more rapidly, a large amount of time should be uselessly spent on the counting operation. This results in spending much time to obtain the copied recording paper through the copying operation succeeding thereto.